[Talk-transit] Multiple tracks

[Peter Miller]

On 22 Jun 2009, at 07:51, Jochen Topf wrote:

> On Sun, Jun 21, 2009 at 05:09:35PM +0100, Richard Mann wrote:
>> No, simpler than that:
>>
>> tracks=1 => render a single line at all zooms
>> tracks=2 => render a double line at all zooms
>> tracks=X => render a multiple line with X tracks at all zooms
>> tracks=1ofX => render a single line at high zooms, but render as if  
>> tracks=X
>> at medium/low zooms
>
> But then you'd still draw several lines nearly on top of each other  
> in medium
> zoom levels which doesn't look good, which was the problem we were  
> trying to
> fix?
>
> Anyway, this is a rather specialized trick about rendering the  
> number of tracks
> properly. But what if you want to render other attributes. Say one  
> of your two
> tracks is an industrial railway, the other a normal passenger  
> railway and you
> want to distinguish those types. On medium zoom levels, is this a  
> two track
> thing and we loose the type distinction, or do we keep it?

The dual_carriageway and Junction relations would appear to the a good  
way of doing such things. I realise that the 'dual carriageway' term  
is not right and that other work would be required on the  
specifications, however it would seem a better starting point.

http://wiki.openstreetmap.org/wiki/Relations/Proposed/Junctions
http://wiki.openstreetmap.org/wiki/Relations/Proposed/Dual_carriageways

A group of parallel tracks would be combined using 'dual carriageway'  
and then a group short sections of track and nodes can be combined as  
a 'Junction'. The render would then have a choice of drawing modes,  
either a single line and single point, or multiple lines/points.



Regards,



Peter


>
>
> Jochen
> -- 
> Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/   
> +49-721-388298
>
>
> _______________________________________________
> Talk-transit mailing list
> Talk-transit at openstreetmap.org
> http://lists.openstreetmap.org/listinfo/talk-transit